Notorious hate preacher Abu Walaa, described as the Islamic State group's de facto leader in Germany, goes on trial Tuesday accused of radicalising young men and running a jihadist network linked to the Berlin Christmas market attacker.

Big W's general manager Teresa Rendo has denied the absence of the word "Christmas" from their stores' artificial tree packaging is "politically correct", as outrage continues over the controversial decision.

Bushfire watch continues as heat remains

Authorities will be keeping a close eye on bushfires across NSW as the heatwave is expected to continue into next week while a brief reprieve is forecast for Sydney and the state's south on Thursday.

Despite the heat across the state on Wednesday, with temperatures across western Sydney above 40C and an alarming 46C in Bourke, none of the 30 ongoing fires monitored by the Rural Fire Service were considered to pose immediate danger.

After a cool change across Sydney and southern NSW on Thursday, temperatures are set to soar back above 40C on Friday and continue into mid next week.

Coastal areas around the city are due for a milder maximum of 27C on Thursday and it's forecast to hit 30C in the west.